This invention relates to a dynamoelectric machine rotor and, more particularly, to a dynamoelectric machine rotor with a permanent magnet type field magnets for use in a synchronous machine.
FIG. 11 illustrates one example of a conventional dynamoelectric machine rotor or permanent magnet type disclosed in Japanese Utility Model Laid-Open No. 3-39355. In FIG. 11, reference numeral 1 designates a rotor 1 in which a permanent magnet 3 magnetized in an axial direction is secured on a rotary shaft 2. On the both sides of the permanent magnet 3, magnetic yokes 4 and 5 are secured to the rotary shaft 2. Claw poles 4a and 5a axially extend from the outer circumference of the magnetic yokes 4 and 5. The axial dimension of a surface of the claw poles 4a and 5a facing to the stationary iron core (not shown) through an air gap is arranged to vary in a sine wave fashion in the circumferential direction. This causes the intersecting magnetic flux passing through the stator winding (not shown) to vary as a sine wave in accordance with the change of the facing surface of the claw poles 4a and 5a.
In the conventional permanent magnet type rotor as above described, the magnetic flux generated from the permanent magnet 3 passes through the magnetic yoke 4, the claw pole 4a and an air gap and into the stationary iron core so that it intersects with the stationary winding. In this case, since a magnetic circuit extending from the magnetic yoke 4 to the outer circumference surface facing the inner surface of the stator iron core of the claw pole 4a has a different cross-sectional area and a different magnetic path length, the magnetic fluxes generated from the outer surface of the air gap are not constant. Therefore, even when the claw poles are modified into a sine wave configuration, the magnetic flux intersecting with the stator winding does not accurately vary as a sine wave and is distorted, This causes a non-smooth varying rotation torque when the rotor is used in an electric motor and generation of magnetic noise when the rotor is used in a generator. Also, the outer circumference of the claw poles 4a and 5a have different magnetic flux densities, i.e., an increased magnetization portion and a decreased magnetization portion appear due to the armature reaction by the energized stator windings, so that the output power is disadvantageously decreased.